In the following patent document 1, for example, there is disclosed a pneumatic tire whose tread portion is provided in middle land zones with narrow grooves.
Such narrow grooves may serve a function in discharging water in part, while maintaining the rigidity of the middle land zones. In the middle narrow groove of the patent document 1, however, a small groove width of less than 2 mm continues along the length of the groove. Therefore, in the ground contacting patch of the tire, the opposite walls of the narrow groove tend to contact with each other in their substantially whole area. Accordingly, the narrow grooves can not serve for drainage, and aquaplaning phenomenon is liable to occur when running on wet roads at high speed. Thus, in order to satisfy both of wet performance and steering stability on dry roads, the pneumatic tire of the patent document 1 has room for improvement.